Heat insulator and fastening structure for same

ABSTRACT

A heat insulator fastening structure includes: a heat insulator which is configured so as to cover an exhaust manifold; and fasteners which are configured so as to fasten the heat insulator to an object to which the heat insulator is to be fastened, the heat insulator being fastened so as to be displaceable in a predetermined range. The heat insulator has: a single first region which is configured so as to vibrate in the same phase; and a single second region which is different from the first region and which is configured so as to vibrate in the same phase. At least one of the fasteners fastens the first region to the object to which the heat insulator is to be fastened. At least another one of the fasteners fastens the second region to the object to which the heat insulator is to be fastened.

TECHNICAL FIELD

The present invention relates to a heat insulator and a fastening structure for the heat insulator.

BACKGROUND ART

A vehicle such as an automobile is provided with a heat insulator, which is arranged to cover the exhaust manifold. The heat insulator shields heat radiated from the exhaust manifold of the internal combustion engine so that the heat does not affect other components. The heat insulator is fastened to a fastening target object at predetermined fastening target sections not to fall off from the vehicle. Patent Document 1 discloses a bead formed for absorbing a vibration around fastened portions of the heat insulator.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Laid-Open Patent Publication No. 2007-113479

SUMMARY OF THE INVENTION Problem that the Invention is to Solve

In a case in which a heat insulator is fastened to a number of fastening target object sections, if fastened portions of the heat insulator vibrate in different phases, the amounts and the timings of displacement of the fastened portions toward and away from the fastening target sections are different from one another. As a result, it is unavoidable that torsion, tension, and compression occur between the fastened portions of the heat insulator. The torsion, tension, and compression may result in cracks between the fastened portions.

It is an objective of the present invention to provide a heat insulator and a fastening structure that limit the formation of cracks between the fastened portions of the heat insulator.

Means for Solving the Problems

To achieve the objective, a heat insulator fastening structure includes a heat insulator adapted to cover an exhaust manifold and a plurality of fasteners adapted to fasten the heat insulator to a fastening target object in a manner in which the heat insulator is movable within a predetermined range. The heat insulator includes a first area, which is adapted to vibrate in a single phase, and a second area, which is different from the first area and is adapted to vibrate in a single phase. The first area is fastened to the fastening target object with at least one of the fasteners. The second area is fastened to the fastening target object with at least another one of the fasteners.

To achieve the objective, a heat insulator is adapted to cover an exhaust manifold and be fastened to a fastening target object with a plurality of fasteners in a manner in which the heat insulator is movable within a predetermined range. The heat insulator includes a first area having a fastened portion adapted to vibrate in a single phase and be fastened to the fastening target object with at least one of the fasteners and a second area having a fastened portion adapted to vibrate in a single phase and be fastened to the fastening target object with at least another one of the fasteners.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an entire heat insulator;

FIG. 2 is a cross-sectional view illustrating the structure of a fastener; and

FIG. 3 is a graph showing changes in the stress applied to the heat insulator relative to changes in the rotational speed of an internal combustion engine.

MODES FOR CARRYING OUT THE INVENTION

The fastening structure of a heat insulator according to one embodiment will now be described with reference to FIGS. 1-3.

As shown in FIG. 1, a heat insulator 1 covers an exhaust manifold 2, which is connected to an internal combustion engine and a muffler and receives vibration transmitted from the internal combustion engine and the muffler. The heat insulator 1 is fastened with fasteners 3 to predetermined fastening target sections P1-P4 of the exhaust manifold 2, which is a fastening target object. The heat insulator 1 is fastened with the fasteners 3 to the fastening target sections P1-P4 in a manner in which the heat insulator 1 can be displaced within a predetermined range. The heat insulator 1 includes a first area A1 and a second area A2. The vibration transmitted from the exhaust manifold 2 vibrates the first area A1 in a single phase and vibrates the second area A2, which is an area different from the first area A1, in a single phase. The first and second areas A1 and A2 of the heat insulator 1 are fastened to the fastening target sections P1-P4 with the fasteners 3. In detail, the heat insulator 1 has two positions in the first area A1 that are fastened to the fastening target sections P1 and P2 and has two positions in the second area A2 that are fastened to the fastening target sections P3 and P4. The first area A1 is located in an upper portion of the heat insulator 1. The second area A2 is located in the center in the up-down direction of the heat insulator 1. In other words, the first area A1 is located at one of two opposite end portions in the heat insulator 1, and the second area A2 is located in the center between the end portions.

As shown in FIG. 2, each of the fasteners 3 for fastening the heat insulator 1 to the fastening target sections P1-P4 includes a support 4 and a bolt 5. The support 4 supports a portion in the corresponding area A1 (A2) of the heat insulator 1 that corresponds to the corresponding fastening target section P1 (P2, P3, P4) such that the supported portion is movable within a predetermined range. The bolt 5 fixes the support 4 to the fastening target section P1 (P2, P3, P4). The support 4 includes a cylindrical body 7. The cylindrical body 7 passes through a hole 6, which is formed in the portion of the heat insulator 1 that corresponds to the fastening target section P1 (P2, P3, P4). A ring-shaped washer 8 fits to the outer circumference at one end in the axial direction of the cylindrical body 7. A flange 9 is formed on the outer circumference at the other end of the cylindrical body 7. Elastic bodies 10 are fixed between the washer 8 and the flange 9 and support a portion around the hole 6 of the heat insulator 1. The bolt 5 passes through the cylindrical body 7 of the support 4 and is screwed into the fastening target section P1 (P2, P3, P4) of the exhaust manifold 2 so that the heat insulator 1 is fastened to the fastening target sections P1 (P2, P3, P4) with the fastener 3. This state allows the heat insulator 1 to be displaced by an amount corresponding to the amount of elastic deformation of the elastic bodies 10 in the support 4.

Operation of the fastening structure in the heat insulator 1 will now be described.

FIG. 3 is a graph that shows changes in a stress applied to a predetermined location (e.g., a location PX of FIG. 1) in the heat insulator 1 at vibration due to changes in the rotational speed of the internal combustion engine. The long dashed double short dashed line in FIG. 3 represents a stress applied to the location PX when it is assumed that the outer rim of the heat insulator 1 is fastened to the exhaust manifold 2 at multiple positions (e.g., eight positions) that are located at predetermined intervals. In this case, when the fastened portions of the heat insulator 1 vibrate in different phases, the amounts and the timings of displacement of the fastened portions toward and away from the fastening target sections of the exhaust manifold 2 are also different from one another. This results in excessive torsion, tension, and compression between the fastened portions of the heat insulator 1, and the stress applied to the location PX becomes stronger as shown in FIG. 3 as indicated by the long dashed double short dashed line.

In contrast, the solid line of FIG. 3 represents a stress applied to the location PX when the fastening structure of the heat insulator 1 of FIG. 1 according to the present embodiment is employed. Even in this fastening structure, the phase of a vibration in the first area A1 of the heat insulator 1 may differ from the phase of a vibration in the second area A2. In this case, the amount and timing of displacement of the fastened portions of the heat insulator 1 toward and away from the fastening target sections P1 and P2 caused by a vibration in the first area A1 are different from the amount and timing of displacement of the fastened portions of the heat insulator 1 toward and away from the fastening target sections P3 and P4 caused by a vibration in the second area A2.

However, the heat insulator 1 is merely fastened to the fastening target sections P1-P4 of the exhaust manifold 2 in the single first area A1 and the single second area A2. Moreover, the first area A1 and the second area A2 of the heat insulator 1 are fastened to the fastening target sections P1-P4 with the fasteners 3. In this fastened state, the heat insulator 1 can be displaced within the range defined by the fasteners 3.

A vibration of the first area A1 and a vibration of the second area A2 cause the fastened portions to be displaced toward and away from the fastening target sections P1-P4. Even if the amounts and the timings of such displacement vary between the fastened portions, the incidence of excessive torsion, tension, and compression is limited between the fastened portions in the first area A1 and the fastened portions in the second area A2. As a result, a stress applied to the location PX of the heat insulator 1 is maintained low as shown in FIG. 3 as indicated by the solid line.

The above-illustrated embodiment achieves the following advantages.

(1) When the heat insulator 1 is fastened to the fastening target sections P1-P4 with the fasteners 3, excessive torsion, tension, and compression between the fastened portions of the heat insulator 1 may result in cracks, but the formation of such cracks is limited. Since the formation of cracks is limited, the heat insulator 1 can be formed with a thin and soft material.

(2) The number of parts for fastening the heat insulator 1, i.e., fasteners 3, is reduced.

(3) The first area A1 is located in an upper part of the heat insulator 1, while the second area A2 is located in the center in the up-down direction of the heat insulator 1. In this case, the distance between the fastened portions in the first area A1 and the fastened portions in the second area A2 of the heat insulator 1 is increased. Thus, even if vibrations of the first area A1 and the second area A2 cause differences in the amount and the timing of displacement of the fastened portions toward and away from the fastening target sections P1-P4, the influence caused by the differences does not easily affect the portion between the fastened parts in the first area A1 and the fastened parts in the second area A2.

(4) The heat insulator 1 has two positions in the first area A1 that are fastened to the fastening target sections P1 and P2 with the fasteners 3, and has two positions in the second area A2 that are fastened to the fastening target sections P3 and P4 with the fasteners 3. Since the first area A1 and the second area A2 each have two positions to be fastened, the heat insulator 1 is fastened to the fastening target sections P1-P4 without a stress concentrating around only one fastener 3 in each of the areas A1 and A2.

(5) The heat insulator 1 is fastened with the fasteners 3 to the fastening target sections P1-P4, which are located on the exhaust manifold 2. A vibration transmitted from the internal combustion engine, a vibration transmitted from the muffler, and temperature changes by receiving heat of exhaust gas associated with the cylinders of the internal combustion engine complicate the vibrations in the exhaust manifold 2. For this reason, vibrations in the first area A1 and the second area A2 of the heat insulator 1 are likely to cause differences in the amount and the timing of displacement of the fastened portions toward and away from the fastening target sections P1-P4. The difference may result in excessive torsion, tension, and compression between the fastened portions in the first area A1 and the fastened portions in the second area A2 to cause cracks, but the formation of such cracks is limited.

The embodiment may be modified in the following forms.

The heat insulator 1 may be fastened to the internal combustion engine and the body of the vehicle. In other words, the heat insulator 1 may be fastened to a fastening target object other than the exhaust manifold 2.

The heat insulator 1 may be fastened with fasteners 3 at two positions in the first area A1 and at only one position in the second area A2. Alternatively, the heat insulator 1 may be fastened with fasteners 3 at two positions in the second area A2 and at only one position in the first area A1.

The heat insulator 1 may be fastened with fasteners 3 at three or more positions in the first area A1 or at three or more positions in the second area A2. 

1. A heat insulator fastening structure comprising: a heat insulator adapted to cover an exhaust manifold; and a plurality of fasteners adapted to fasten the heat insulator to a fastening target object in a manner in which the heat insulator is movable within a predetermined range, wherein the heat insulator includes a first area, which is adapted to vibrate in a single phase, and a second area, which is different from the first area and is adapted to vibrate in a single phase, the first area is fastened to the fastening target object with at least one of the fasteners, and the second area is fastened to the fastening target object with at least another one of the fasteners.
 2. The heat insulator fastening structure according to claim 1, wherein the heat insulator is adapted to be fastened to the fastening target object only in the first area and the second area.
 3. The heat insulator fastening structure according to claim 1, wherein the first area is located at an upper portion of the heat insulator, and the second area is located in a center in an up-down direction of the heat insulator.
 4. The heat insulator fastening structure according to claim 1, wherein the heat insulator has two opposite end portions and a central portion located between the end portions, the first area is located in one of the end portions, and the second area is located in the central portion.
 5. The heat insulator fastening structure according to claim 1, wherein the heat insulator is fastened to the fastening target object at two positions in the first area and is fastened to the fastening target object at two positions in the second area.
 6. The heat insulator fastening structure according to claim 1, wherein the heat insulator is fastened to the fastening target object at two positions in the first area and is fastened to the fastening target object at one position in the second area.
 7. The heat insulator fastening structure according to claim 1, wherein the fastening target object is the exhaust manifold.
 8. A heat insulator, which is adapted to cover an exhaust manifold and be fastened to a fastening target object with a plurality of fasteners in a manner in which the heat insulator is movable within a predetermined range, the heat insulator comprising: a first area having a fastened portion adapted to vibrate in a single phase and be fastened to the fastening target object with at least one of the fasteners; and a second area having a fastened portion adapted to vibrate in a single phase and be fastened to the fastening target object with at least another one of the fasteners. 